Frequently Asked Questions

Net free area is the standard of
measurement used by the ventilation industry. It is
the unobstructed area of a ventilator through which air may flow. For example, a C816 cornice vent (a 16” X
8” vent) has a NFA of 65 square inches. The hole cut for this vent would be 15
inches long by 7 inches wide. The area of
the opening would be 105 (15 X 7) square inches, but the net free area of a
Lomanco C816 is 65 square inches. The louvered section and screening hinder the
air flow and their net free area is lessened by their measurements.